Sandproof pump



B. F. SCl-IMH'DTy SANDPROOF PUMP April 3, 1934.

Filed Nov. 29. 1930 6 lSheecs--Sheet 1 B. F. SCHMIDT SANDPROOF PUMP 6 Sheets-Shaml 2 Filed Nov 29 April 3, 1934. B. F. SCHMIDT 1,953,439

SANDPROOF PUMP Filed Nov. 29, 195o esmas-sheet s 6 Sheets-Sheet 4 B. F. SCHMIDT 1,953,439

SANDPROOF PUMP Ap 'h 3, 1934.

Filed Nov. 29,` 195o e sheets-sheet 5 B. F. SCHMIDT 'April 3, ,1934.-

SANDPROOF PUMP Filed Nov. 29 e sheets-sheet e and tn/552| s 9 claims.

Patented pr. 3, 19324` PATENT OFFICE SANDPROOF PUMP Benjamin F. Schmidt, Los Angeles, Calif.

Application November 29, 1930, Serial No. 498,943

This invention relates to pumps and particularly pertains to sand proof pumps. of the type including a piston reciprocable in a body of mercury or other protective liquid of greater density than a fluid to be pumped, and more especially appertains to improvements in pumps of the character set forth in my copending application for United States Letters Patent, Serial Number 465,835, iled July 7, 1930.

An object of the invention is to provide a pump of the reciprocal piston type in which the piston is so arranged as to be protected by a body of liquid, such as mercury, entrapped within the,

pump casing in such manner as to inhibit the passage of sand or other granular substances contained in the fluid being pumped from passing between the contiguous wearing surfaces ofthe piston and the4 walls of the pump, and whereby the discharge of sand or other granular solids associated with the fluids in the pump will be facilitated.

Another object is to provide a pump of the above character which is so formed as to maintain a protective liquid in and around a hollow or tubular pump piston in substantially predetermined proportions interiorly and exteriorly thereof and whereby the possibility of loss of the protective liquid during operation of the pump will be obviated.

With the foregoing objects in view, together with such other objects and advantages as may subsequently appear, the invention resides in the parts and in the combination, construction and arrangement of parts hereinafter described and claimed and illustrated by way of example in the accompanying drawings, in which:-

Fig. 1 is a View in vertical section partly in elevation of a pump and with parts broken away, illustrating a simple embodiment of the invention, the pump piston being shown in its lowermost position;

Fig. 2 is a diagrammatic view of the pump shown in Fig. l as seen in section and elevation on a reduced scale for illustrating the mode of operation of the pump;

Fig. 3 is a view similar to that of Fig. 2, but showing the pump piston in an elevated position;

ig. 4 is a detail in cross section as seen on the line 4-4 of Fig. 1;

Fig. 5 is a detail in cross section as seen on the line 5--5 of Fig. 1;

Fig. 6 is a detail in cross section as seen on the line 6--6 of Fig. 1;

Fig. 7 is a detail in cross section as seen on the line '7-7 of Fig. 1;

(Cl. 10S-204) Fig. 8 is a view in vertical section of a pump with parts broken away illustrating another form of the invention, and showing the pump piston in its lowermost position;

Fig. 9 is a diagrammatic view in sectionand elevation of the pump shown in Fig. 8 on a reduced scale showing the piston in its lowermost position;

Fig. 10 is a view similar to Fig. 9 showing the piston in an elevated position; l

Fig. 11 is a detail in cross section taken on the line 11-11 oi Fig. 8;

Fig. 12 is a view in elevation taken on the line 12-12 of Fig. 11;

Fig. 13 is a view in vertical section as seen on 70 the line 13--13 of Fig. 12 with parts removed indicated in dotted lines;

Fig. 14 is a View inv horizontal section taken on the 4line 14-14' of Fig. 8;

Fig. 15 is a view in vertical section of a pump with parts broken away illustrating another modied form of the invention, showing the pump piston in its lowermost position;

Fig. 16 is a diagram of the pump shown in Fig. 13 on a reduced scale, illustrating the piston in its lowermost position;

Fig. 17 is a View similar to Fig. 16 showing the piston in an elevated position;

Fig. 18 is a View in horizontal section -and plan-as seen on the line 18-18 of Fig. v15;

Fig. 19 is a view in horizontal section as seen on the line 19--19 of Fig. 15;

Fig. 20 is a View in horizontal section as seen on the line 20-20 of Fig. 15;

Fig. 21 is a view in vertical section o f a pump with parts broken away illustrating another form of the invention, showing the pump piston as disposed in its lowermost position;

Fig. 22'is a view in vertical section of the pump shown in Fig. 21 illustrating the piston in an elevated position;

Fig. 23 is a detail in horizontal section as seen on the line 23-23 of Fig. 21;

Fig. 24` is a view in elevation as seen on line 24-24 of Fig. 23;

Fig. 25 is a view in vertical section taken on the line 25--25 of Fig. 24, with parts removed indicated in dotted lines;

Fig. 26 isa view inhorizontal section taken on the line 26--26 of Fig. 21;

Fig. 27 is a view in Vertical section with parts broken away showing a further modied form of the pump;

Fig. 28 -is a view in vertical section of the pump shown in Fig. 27 illustrating it with the piston in its lowermost position;

Fig. 29 is a View similar to that of Fig. 28 showing the piston as disposed in its uppermost position;

Fig. 30 is a view in horizontal section taken on the line 30-30 of Fig. 27;

Fig. 31 is a view in section and elevation illustrating the portion of the piston shown in Fig. 30 in elevation;

Fig. 32 is a view in horizontal section taken on the line 32-32 of Fig. 27;

Fig. 33 is a view in horizontal section taken on the line 33-33 of Fig. 27;

Fig. 34 is a View in vertical section with parts broken away showing further modified form of a pump embodying the invention;

Fig. 35 is a diagram in vertical section and elevation illustrating the pump shown in Fig. 34 on a reduced scale illustrating the pump piston in its lowermost position;

Fig. 36 is a View similar to that in Fig. 35 showing the piston in its uppermost position;

Fig. 37 is a detail 'in horizontal section taken on the line 37-37 of Fig. 34;

Fig. 38 is a view in elevation as seen on the line 38--38 of Fig. l37;

. Fig. 39 is a view of the detail shown in Fig. 38 in the direction indicated by the arrow 39, with parts broken away;

Fig. 40 is a detail in horizontal section as seen on the line 40-40 of Fig. 34.

Referring to the drawings more specically, in which corresponding reference characters indivcate corresponding or similar elements in the several views, A indicates a pump casing which has a lower end wall 41 formed -with an intake opening 42; the end wall 41 being here shown as comprising a plug which is threaded into the pump casing, and from which bottom wall 41 is erected an intake tube B, the lower end of which is shown as screwed into engagement with the intake opening 42. The tube B projects upwardly into the pump casing A and terminates in suitable spaced relation from the bottom wall 41, and has its outer periphery spaced from the inner periphery of the pump casing in concentric relation thereto; the casing A and tube B being cylindrical in form.

Reciprocally mounted within the pump casing A and surrounding the intake tube B is a tubular piston C carried on a pump rod D; the interior of the piston being in open communication at the lower end thereof with the interior of the pump casing. The tube B and piston C are of such lengths relative to the elected length of stroke of the piston that the lower end portion of the latter is maintained at all times during operation of the pump interposed between the tube B and the casing A, and the piston is so arranged that when in its lowermest position, its lower end will be disposed adjacent the bottom wall of the pump casing.

Entrapped within the lower portion of the pump casing is a body of suitable protective liquid F having a density or specic gravity exceeding that of a uid to be pumped and sufficient to oat granular solids associated with such fluid, and which liquid F is insoluble in the fluid being pumped. For the purpose of brevity, this liquid F will be hereinafter referred to as mercury.

The mercury body F is coniined in the space between the tube Band the pump casing A and extends on opposite sides of the lower portion of the piston' C to produce a mercury column G interiorly of the piston occupying a space between the lower portion of the piston and the tube B, and also to afford a mercury column H exteriorly of the piston occupying the space between the lower portion of the piston and the pump casing A.

The relative levels of the mercury columns G and H will vary during reciprocation or? the piston by reason of displacement of the mercury body during movement of the piston, but the present invention contemplates the provision of a means or construction whereby the relative volumes of the mercury columns G and H will be maintained substantially uniform or will be caused to assume definite relations from time to time in event of any variation in their relative volumes, and whereby the levels ofthe mercury columns G and H will be caused to lie on substantially predetermined planes when the piston is disposed in its lowermost position.

A seal E is provided between the piston and the pump casing which may be of any suitable construction.

In the form of the invention shown in Figs. 1 to 7 inclusive, the upper end of the intake tube B is fitted with a normally closed upwardly opening foot valve J, here shown as comprising a ball 43 arranged in a cage 44 carried on the upper end of the tube B, and which ball normally rests by gravity on a seat 45 whereby communication between the intake tube B and the interior of the piston C is normally closed on down stroke of the piston and when the piston is at rest, but which is open on up-stroke of the piston to admit fluid being pumped to the interior of the piston.

The upper end of the piston C is formed with a passage 46 which leads from the interior of the piston to the exterior thereof, and which passage is tted with an upwardly opening valve K here shown as comprisinga ball 47 which normally rests on a valve seat 48 thereby normally closing the passage 46 during up-stroke of the piston and when the piston isA at rest, but which moves off the seat to open the passage 46 when the piston is moving on its down stroke.

The piston C includes a cylindrical shell 49 having an externally threaded tubular extension 50 on its lower end, on which is mounted the seal E here shown as comprising a series of cup leathers 51 held in place by crowding rings 52 screwed onto the threaded extension 50. The cup leathers are so arranged that on up-stroke of the piston they will effect such close contact with the walls of the pump casing A as to effect lifting of the column of liquid in the pump casing thereabove. The column H of the mercury extends above the cup leathers 51 a distance exceeding the length of stroke of the piston and is carried with the latter during the stroke thereof so as to maintain a body of mercury between the liquid being pumped and the piston cup leathers 51, and the mercury column H is of such length in excess of the length of the piston stroke that such volume of mercury as may pass the cup leathers will not lower the level of said mercury column H to a point such that liquid in the well casing above the mercury column will be lowered sufciently to contact the portion of the pump casing contacted at any time by the cup leathers.

The operation of the pump just described isas follows: On upstroke of the piston C, a suction is induced interiorly of the latter'such as to effect intake of the liquid or uid to be pumped from intake tube B through the valve J. which body of liquid accumulates on top of the mercury GQ11111111 G and is confined within the piston C during the upstroke of the latter. The seal E will then act to elevate the mercury column H and the column of fluid thereon previously delivered to the well casing to effect discharge of a portion of such fluid. On upstroke of the piston, the level of the mercury colunm G will fall so that when the piston is in its uppermost position, the level of the mercury column H will be above that of the mercury column G as illustrated in Fig. 3.v By reason of there then being a negative pressure on the mercury column G, and a head pressure on the mercury column H, a portion of the mercury from the column H may be forced downwardly past the cup leathers 51 and added to the volume of the mercury body beneath the piston. It is apparent that if the seal between the piston and cylinder walls was sufciently tight, the column H of mercury above the cup leathers would be maintained constant at all times, and there would be no passage of mercury downwardly past the cup leathers. However, this would be practically impossible to construct, as to form the cylinder or pump casing free of small pockets can not be readily effected, and hence some slight leakage of mercury downwardly past the seal E will necessarily take place. In fact it is desirable that suicient loose fit or clearance be provided to'.permit such ow of mercury past the seal when the piston is in its lowermost position so as to permit the mercury to seek its own working level both inside and outside ofthe piston.

On downstroke of the piston, the valve J is closed and valve K opens to perr'nit iiuid therebeneath to ow upwardly through the passage 46 into the pump casingabov the plunger where it is entrapped and subsequently elevated and advanced to discharge by the repeated upstrokes of the pump piston in the manner common to pumps of the reciprocal piston type. As the piston moves downwardly, it displaces a portion of the mercury body F, thereby causing the mercury column G to rise in the piston around the tube B so that the level of the mercury column G will then be spaced above the level of the outer mercury column H.

'Ihe length of the intake tube B is such in relation to the length of the mercury column G that when the surface of the latter is elevated to its uppermost position, as is the case when the piston C is in its lowermost position, as illustrated, for example, in Fig. 2, the mercury will by no chance reach the valve K, so that the latter will at all times be submerged in the uid being pumped.

During the downstroke of the piston, the fluidx pressure interiorly and exteriorly thereof will be equalized by reason of the valve K being, then open and the valve J then closed. It follows that in event the mercury column G has been mate'- rially increased by the addition thereto of mercury from the column G `during the upstroke of the piston an added weight will be imparted to the column G which will tend to force a portion of the mercury body upwardly past the cup leathers and thereby replace such mercury as was previously forced downwardly past the seal E; the mercury thus seeking and establishing its normal and corresponding levels interiorly and exteriorly of the piston when the latter reaches its lowermost position.

In the form of the invention shown in Figs. 8 to 14, inclusive, the intake tube B is shown as tted at its lower end with a second foot valve M comprising a ball 53 arranged in a cage 54 lpast the ball valve 61 will cause the latter to and normally resting on a seat 55 to close the lower end of the intake tube B. v The upper end of the tube B is equipped with the foot valve J as before described. By thus providing a pair of foot valves at opposite ends of the tube B, the latter will be filled with the fluid being pumped during down stroke of the piston to obviate formation of a partial vacuum within the intake tube which under some conditions might tend to effect collapse of the latter.A

Another feature ormodication, illustrated in Figs. 8 to 14 inclusive, is the provision of a valve controlled passage in the walls E of the piston C affording a communication between the mercury columns G and H, and which passage is here shown as formed by a valve casing 56 extending through an opening in the piston wall and having screw engagement therewith. The valve casing 56 includes a back wall 57 in which is formed an opening 58 leading to the interior of the piston, and mounted on the casing 56 isv a face plate 59 formed with an opening 60 which leads to the exterior of the piston, and formed on the back of the face plate 59 is a wall 61 which partitions the interior of the housing 57 into two compartments 62 and 63; the compartment 62 communicating with the opening 58, and the compartment 63 communicating with the opening 60.

Arranged in the compartments 62 and 63 are ball valves 64 and 65 which are adapted to rest on valve ports 66 and 67 at the end of a passage 68 leading beneath the wall 61. 'I'his valve controlled passage may be located anywhere in the piston below, however, the point at which the mercury columns may rise when at their peak, but is here shown as located just above the seal E. By this arrangement the ball valve 64 is exposed to the internal mercury column G while the ball 64 is exposed to the external column H, and it follows since both columns of mercury` are always above-the valve, vboth of the valves Aare inclined to float when the mercury pressure only' is upon them and the pressures interiorly and exteriorly of the piston are balanced, as illus trated in Fig. 9. The ball valves 64 and 65 would then be clear of the ports 66 and 67 and accordingly an open communication would then be afforded between the opposite sides of the piston wall through the opening 58, chamber 62, port 66, passage 68, port 67, chamber 63, and opening 60, and accordingly the mercury columns will then meet corresponding levels through this communication. The moment the piston C starts to rise from its lowermost position, as shown in Fig. 9, there will be a rapid change of pressure on the mercury columns G and H due to a partial Void inside the piston with high pressure exteriorly of the piston. The rapid rush of mercury then occasioned through the opening 60 advance to its seat and be there held until the piston reaches its uppermost position, then just as the piston proceeds to descend and the valve K opens, then the pressures interiorly of the piston are equalizedan'd by reason of the mercury column H then extending above the mercury column G interiorly of the piston, as shown in Fig. 3, mercury from the column G will flow from the outside columnfH to the inside column G past the valves and 64, respectively, until thel 1 piston reaches its midstroke.

After the piston has reached the center of its downward stroke, the mercury will flow fromthe inside column G to the outside column H and will continue to do so until the piston has 1 reached the bottom of its downward stroke at which time both columns of mercury will be on a levelv with each other or nearly so. This movement of the mercury from the inside of the piston and then out, as above described, takes place at each stroke of the piston. It may be that under certain conditions the mercury column will be inclined to hold the ball valve in the closed position until the piston-has descended to the pointwhere the two columns of mercury are almost equal, at which time due to the balance pressures, both ball valves will oat and the mercury will then be permitted to ow in or out as the levels may require.

Another feature, illustrated in Figs. 8, 9, and 10 is the provision of a shield extending over the upper end of the piston and having an apronf 71 which surrounds the upper end portion of the piston and extending downwardly to a `point contiguous the normal level of 'the mercury column H; the shield being formed at its upper end with.. outlet openings 72 formed with downwardly projecting lips 73 on their lower margins adapted to deflect a portion of the upgoing stream of fluid being pumped downwardly between the apron 71 and the upper portion of the piston and around the lower margin of the apron 71 thereby agitating the portion of the uid being pumped supported on the mercury column H and` thereby preventing the excessive settling of solid particles on top cf. the mercury column H. y

In the modif-led form of the invention shown in Figs. 15 and 20 inclusive, the piston C is formed with an internal downwardly extending tubular portion 75 which telescopes the upper end of the intake tube B and connects with a transverse partition 76 constituting the top wall of the piston and which partition r-is formed with a plurality of openings 77 normally closed by ball valves 78 seating on the upper margins thereof. The piston side walls are formed with openings 79 contiguous the ball valves 78 which in event the mercury column G becomes of sufficient height to unseat the balls 78 when the piston is' in its lowermost position, the excess mercury from the column G will flow into the space between the piston and the pump casing and will be added to the mercury column `H to reestablish the level of the mercury column H and thereby compensate for such mercury as may have been forced past the seal E during the upstroke of the piston.

The valves 78 also cooperate with the valve J in permitting the ow of the fluid being pumped from the interior to the exterior of the piston. The valve K in this instance might be dispensed with, but is desirable in that it will serve the pur-.

pose of preventing the entrapment of gas within the intake tube where the pump is employed in a well containing gas under pressure.

Furthermore the ball valves 78 will also serve as agitators to prevent settling of solid particles on the mercury column because of Vtheir proximity to the mercury levels.

In the arrangement shown in'Fig. 15, the fotj valve J is located adjacent the lower end of the intake tube, which construction may be employed where the relation o-f the upper end of the intake tube4 and the mercury level is such as to yprevent any vpossibility of mercury entering the f upper end of the tube B.

In the modifications shown in Figs. 21 to, 26 inclusive, the valve controlled passage previously described in Figs. 8 to 14 inclusive, is shown as located in the piston at the uppermost point to which the mercury column G interiorly of the piston may rise; Figs. 23, 24, and 25 substantially corresponding to Figs. 11, 12, and 13 for illustrative purposes in conjunction with the showing in Fig. 21, and the parts being given corresponding reference characters, as the description applied to Figs. 8 to 13 is applicable here. However, in this arrangement, the operationof the valves 64 and 65 would be different since the ball valves would float only when the mercury to effect opening of the valves as before described. l

In Fig. 21, a modified constructiony of the seal E on the lower end of the piston is shown; the seal being formed by enlarging the exterior of the lower portion of the piston and fitting this enlarged portion with a piston ring 85, a cup leather 86, and a lubricant receiving chamber 87 located between the cup leather and the piston rlng.

In the modifications shown in Figs. 27 to 33 inclusive, the seal E is formed interiorly of the piston instead of exeriorly thereof and is arranged to coact with the walls of the intake tube B in effecting the pumping action. A further modip cation is shown comprising a by-pass tube 90 located within the intake tube B having its end portions opening through the walls of the tube B through ports 91 and 92; the port 91 opening to the interior of the-piston above the seal E and the port 92 opening to the interior of the pump casing below the piston and beneath the seal E, and located in the by-pass 90 are'oppositely opening valves 93 and 94. The valve 93 is located at the upper end portion of the by-pass 90 and is adapted to be open when submerged in the mercury column G to permit the flow of mercury from the column G downwardly through the by-pass to `be added to the mercury column H when the pistonis in its lowermost position to establish the relative balanced relation between the mercury columns G and H and to compensate for leakage of mercury past the seal.

A further modification resides in a series of angularly disposed blades 95 located on the exterior of the piston which will operate on reciprocation of the latter to maintain the fluid being pumped under a state of agitation to prevent the excessive settling of solid particles into the space surrounding the piston.

In the modified form of the invention shown in Figs. 34 to 40 inclusive, an alternative arrangement of the seal E is shown in which the latter is carried on the upstanding intake tube B instead of on the piston aspreviously described. In this arrangement a series of cup leathers 95 are carried on the tube B and coact with the piston in effecting the necessary seal whereby on upstroke of the piston a suctionis induced interiorly thereof to draw the liquid or fluid being pumped into the interior of the piston through the intake B.

A further modification resides in the provision of downwardly extending tubes 96 and 97 leading from the openings 58 and 60 of the valve controlled passage provided in the piston wall as before described, which tubes serve as'a means for preventing granular material supported on the mercury column from passing to the ball valves 64 and 65; the lower ends of the tubes 96 and 97 opening beneath and being maintained at all times below the upper surfaces of the mercury columns G and H. z

I claim:

1. In a pump, a pump casing, a reciprocal piston therein, a seal formed on said hollow piston, a body of protection liquid above and below said seal arranged to prevent a fluid being pumped from coming in contact with surfaces of the pump with which said seal coacts to effect a pumping action, said liquid being insoluble in the uid' being pumped, an upstanding tube in said casing projecting through said liquid into said piston and terminating above said liquid, and apair of valves one of which is adapted to permit the flow of said liquid from the exterior to the interior of said piston and the other of which is adapted to permit the flow of liquid from the interior to the exterior of said piston.

2. In a pump, a pump casing, a reciprocal piston therein, a seal formed on said hollow piston, a body of protection liquid above and below said piston arranged to prevent a uid being pumped from coming in contact with surfaces of the pump with which said seal coacts to effect a pumping action, said liquid being insoluble in the fluid being pumped and being of sufficient density to float solid particles contained in the fluid being pumped, an upstanding tube in said casing projecting through said liquid into said piston and terminating above said liquid, means for preventing excessive settling and accumulation of solid particles on said liquid, and a pair of valves one of which is adapted to permit the flow of said liquid from the exterior to the interior of said piston and the other of which is adapted to permit the now of liquid from the interior to the exterior of said piston.

. 3. In a pump, a. pump casing, a reciprocal hollow piston therein, a seal on said plunger slidably contacting said casing, a protective liquid in said casing immediately above and below the contiguous slidably contacting portions of said seal and casing, an upstanding tube in said casing projecting through said liquid into said piston and terminating above said liquid, means for eifecting delivery of said liquid between the interior and exterior of said piston above said seal, said means including a pair of valves carried by said piston,

one of which is adapted to permit the ow of said liquid from the exterior to the interior of said piston and the other of which is adapted to permit the ow of the liquid from the interior tothe exterior of said piston. l

4. In a pump, a pump casing, a vertically reciprocal hollow piston therein, a seal on said piston slidably contacting said casing, bodies of protective liquid in said casing above and below the contacting portions of said seal and` casing and affording a body of said liquid in which said seal travels to maintain a fluid shield on opposite sides of and around said seal, an upstanding tube in said casing projecting through said liquid into said piston and terminating above said liquid, and a. pair of normally closed valves carried by said piston for making and breaking communication between the bodies of liquid above said seal, one of said valves being adapted to permit the ow of said liquid from the exterior to the interior of said piston and the other of `which is adapted to permit the ow of said liquid from the interior to the exterior of said piston.

5. In a pump, a'pump casing having au inlet opening at its lower end, an intake tube projecting upwardly into said casing from said inlet opening, a foot valve normally closing said intake tube, a mercury body entrapped in said casing encompassing the lower portion of said tube, a reciprocable hollow piston in said casing having an open lower end, said piston arranged to encompass said tube with the lower portion thereof submerged in said mercury body with portions of the mercury body extending interiorly and exteriorly of said piston, a pair of valves for maintaining a substantially balanced relation between the bodies of mercury interiorly and exteriorly of the piston; one of said valves being adapted to permit the now of said liquid from the exterior to thev interior of said piston and the other of which valves is adapted to permit the flow of the liquid from the interior to the exterior of said piston, a portion of the upper surface of said mercury body being exposed to said casing and on which fluids being pumped are carried, and means for eiecting disturbance of the fluid adjacent the surface of the mercury body during .movement of said piston.

6. In a pump, a pump casing having a bottom wall formed with an intake opening, an upstanding intake tube connected to said opening projecting upwardly in said casing and spaced therefrom, a foot Valve normally closing the passage through said tube, a reciprocal piston in said casing having an open lower end, the lower portion of which encircles said tube, a passage in `the upper portion of said piston aiording a communication between the interior and exterior thereof, a normally closed upwardly opening valve in said passage, a mercury column encircling said tube arranged interlorly of said piston, a mercury column encircling'said piston, and a valve communication between said mercury columns including a pair of valves adaptedto float in the mercury of said columns one of which is adapted to permit the flow of mercury from the inner column to the outer column, and the other of which is adapted to permit the ow of mercury from the outer column` to the inner column, and each of which floatable valves is adapted to close under back pressure imposed thereon.

7. In a pump, a pump casing having a lower end wallformed with an intake opening, an intake 'tube connecting with said opening and leading upwardly into said casing in spaced relation thereto, a foot Valve associated with said tube upwardly opening and normally closed, a hollow piston in said casing having a lower end portion encircling said tube, a seal embodied in said piston, a passage in the upper portion of said piston aiording a communication between the interior thereof and the exterior thereof, an upwardly opening normally closed valve carried by said piston for opening and closing the communication through said passage, a body of sealing liquid entrapped in said casing around said intake tube and extending between the tube and lower portion of said piston and between the walls of the casing and the lower portion of the piston both above and below said seal and arranged to prevent a fluid being pumped from contacting said seal and wall portions of the pump coacting therewith; said liquid being of sufficient density to support on its upper surface solid particles contained in the liquid being pumped and having its upper surface arranged so that solid particles in the liquid being pumped may settle thereon, and a pair of valves one of which is adapted to permit the iiow of said liquid from the exterior to the interior of said piston and the other of which is adapted to permit the ow of liquid from the interior to the exterior of said piston.

8. In a pumpa pump casing, a vertically reciprocal hollow plunger therein the lower portion of which extends contiguous the walls of said casing and the upper portion of which is spaced from said casing, a sealing fluidin the space between said plunger and casing, said plunger being tubular and open at its lower end to said casing, 10 a column of sealing uid in said casing extending internally oi said plunger and terminating intermediate the ends thereof, an intake tube in said casing projecting through said last named column of fluid and opening thereabove interiorly of said plunger, a passage in said plunger leading from the interior of said plunger to the exterior thereof, and aiording a communication between the space between said plunger and casing and the interior of said plunger, a pair of check valves arranged in said passage for controlling the ilow of said sealing iiuid through said passage, one of said valves being adapted to permit the flow of said liquid from the exterior to the interior of said plungerand the other of which valves is adapted to permit the flow of liquid from the interior to the exterior of said plunger.

v9. In a pump, a pump casing having an inlet opening at its lower end, an intake tube projecting upwardly into said casing from said inlet opening, a foot valve normally closing said intake tube, a mercury body entrapped in said casing encompassing the lower portion of said tube, a reciprocable hollow piston in said casing having an open lower end, said piston arranged to encompass said tube with the lower portion thereof submerged in said mercury body with portions of the mercury body extending interiorly and exteriorly of said piston, and means for maintaining a substantially balanced relation between the bodies of mercury interiorly and exteriorly of the piston, including a valve controlling the ow of said liquid from the exterior to theinterior of said piston and a valve for controlling the flow of said liquid from the interior to the exterior of said piston.

BENJAMIN F. SCHMIDT. 

